???? Not to USM, neither fly there, assume you must be talking about SIN/KUL. From memory the biggest aircraft into USM are 734 (TG) and 319 (MI, PG). Assume A320's are too big for TR or 3K (or Air Asia) to fly there, either that or landing fees to expensive.3K and Tiger often have Tuesday specials, worth keeping an eye on.
I've done the reverse of that several times and my experience has been same. subang is a LCC terminal and very basic. But otherwise no issues. Even used their call center who spoke good English and were helpful.I flew them from SIN - Subang and couldn't really fault the flight, it felt just like any other hr long flight in the ATR